Method of preparing alkyl halides



good rates of reactionin the desired direction. ethyl sulfate were slowly added to the heated in aqueous solutions which contain high concenthe removal of water by means of the reflux trations of the metal halides. condenser.

Thus, the invention provides reaction at rela- The product contained 237 grams of ethyl chlolatented Nov. 25, 1941 I 2,263,666

hurrah STATES PATENT OFFICE METHOD or mmrsnmc 'ALKYL nannies Alexander L. Wilson, Pittsburgh, 1a., assignor to Carbide and Carbon Chemicals Corporation, a corporation of New York No Drawing. Application May 5, 1938, Serial No. 206,173

it Claims. (Cl. 260-652) This invention is an improved process for maliof metals yielding insoluble sulfates to induce ing alkyl halides. The process broadly comprises the reaction of both alkyl groupsof the dialkyl the reaction of dialkylsulfates with metal halides sulfates, and the reaction is directed toward the in aqueous solution, and the principal object of alkyl halide rather than toward competing rethe invention is to provide a process of this class 5 actions by the choice of metal halides capable of in which both alkyl groups of the dialkyl sulfate forming aqueous solutions of high molar conare caused to react with halogens while hydrolycentration and whose sulfates do notreduce this sis of the dialkyl sulfate and other side reactions concentration.

are suppressed. The conditions which make pos- Saturated or substantially saturated aqueous sible the achievement of this object include the solutions of the metal halides are preferably'emuse of metal halides which are capable of formployed, and it will be understood that this refers ing aqueous solutions containing high molar conprimarily to saturation at ordinary temperatures, .centraticns of the salt; the use of halides of met since the handling and storage of solutions conals whose sulfates are relatively insoluble in the taming undissolved solids present practical difreaction mixture; and the conduct of the reacl5 ficulties. Of course, by the addition of metal tion at relatively elevated temperatures between halide to the solution heated to its reaction tem- 90" and about 200 C. while maintaining a high perature, the concentration can be increased.

concentration of the metal halide in the aqueous The following examples will serve to illustrate solution. The concentration of themetal halide the invention:

can be lrept high throughout the reaction by dis- Example I tilling water from the solution or by addition of; A saturated solutwn of moles of calcium the metal halide, or by both of these means. Preferably the process is carried out at temperatures of from 100 to about 140 6., and'the salt concentration is kept high by the removal of water & distma'te- These conditions provide while the product was continuously distilled from quantities of the metal ha ide in the reaction the mixture. The distillate contained water and mixture which are considerab yin excess of those 216 moles of ethyl chloride, together with a 5mm required for reaction with both alkyl gmups of amount of diethyl sulfate amounting to 0.065

the diamy1 su1fat9' mole. Some unreacted diethyl sulfate also was The halides of the alkaline earth metals are left in the reaction vessel morehighly soluble in water than those of any The yield of unpurifled ethyl chloride WM other metals and calcium, barium, strontium, 2 th and beryllium halides are intendedfor use in 23 32: based on home grouPs of methyl this invention. The chlorides and bromides of 3 Example H calcium and barium are Preferred. Suitable dialkyl sulfates are the lower members of thi A saturated solution of calcium chloride corn series, such as dimethvl sulfate, diethyl sulfate, taining 10 moles (1119 grams) of the salt and dipropyl and dilsopropy1su1fates,'and dibutyl and 0 r ms of water was hea ed to about c'. diisobuty'l sulfates. l 40 in a vessel provided with a reflux condenser, by

The alkaline earth metals, as a class, form relameans of which water could be removed from the tively insoluble sulfates, and this is particularly 1 distillate, following which more volatile matetrue in the present process wherein the sulfates ria s we pas d t a d ln a r of all of these metals are but very slightly solu Grated receiver- TWO Eldditional 11101.65 ble in the concentrated salt solutionsof the rerams o um h d w then added to action mixture. This fact assists in obtaining the salt solution. Two moles (308 grams) of dichloride was heated to a temperature between and C. in a vessel equipped with a distilling column. Diethyl sulfate in an amount equivalent to 1.24 moles was then slowly added The hydrolysis of dialkyl sulfates to form alcohol solution, which was maintained at a temperature is a reaction competing directly with the desired between 90 and 100 0., the average temperature reaction to form alkyl halides. It has been found, rin the reaction being about 95 C. The vahowever, that this reaction is largely suppressed 1301's evolved were collected inthe receiver after tively high temperatures in solutions of halides 55 ride and 1 am of die hyl sulfate. This is from the distillate.

cover pure ethyl chloride.

chloride or 92% of the theoretical both available ethyl groups.

Example III The data in tabular form below show the apyi'eld. based on plication of this invention to the reactions of CaBr BaCh CaCh BaBr,

I 2. 25 3.0 4.0 2. Diethyl 0. 75' 1. 0 Dimeth .do 0. 87 0.67 Concentration of salt solution percent by weight" 75 34 50 60 Reaction temperature .C 105-110 104 120-125 95-110 Alkyl halide recovered. moles 1. 23 0. 79 l. 43 1. Yield (on the basis of both alkyl groups) ..percent 82 40 83 86 In each instance the dialkyl sulfate was added to the reaction mixture in portions from time to time. Water and the alkyl halideformed .were removed co inuously from each reaction as a distillate. 'i ge alkyl halide was collected in a refrigerated receiver after the removal of water In the reaction involving barium chloride, an aqueous solution containing excess salt was used, and in the reaction of calcium chloride-with dimethyl sulfate a portion at the salt was added to the reaction mixture as the reaction progressed.

Example IV An embodiment of this invention of particular importance is the production of ethyl chloride from calcium chloride and diethyl sulfate. In the tabulated data below, five typical reactions Yield ethyl chloride. ..peroent In each reaction, diethyl sulfate was added continuously and a distillate containing the ethyl chloride together with small quantities of alcohol,

' water and hydrochloric acid was continuously removed. This mixture was redistilled to re- The calcium sulfate formed was virtually/insoluble in the reaction mixture and it was allowed to accumulate in the reaction vessel u 'til the residue become too thick to be readily st in the reaction vessel by filtration. Variations in the procedures specifically outlined-above will be apparent. For example, the dialkylv sulfate and the metal halide may be added in a single batch or both may be added continuously. It is also possible to withdraw the calcium sulfate continuously as it is formed. The calcium chloride may be supplied either in solid form or in aqueous solution. Freeacid which may develop in the reaction mixture can be neu-. tralized if desired by the addition of suitable ed. The calcium sulfate .can be readily removed from the liquid products 2,268,666 equivalent to a yield 013,3.67 moles of the ethyl.

ticularly'efiective for this purpose.

It will be seen that the process of this invention provides a simple and emcient method for making alkyl halides. It is particularly desirable from the standpoint of economy since the alkaline earth metal chlorides, particularly calcium chloride, provide a readily available and cheap source of chlorine.

This application contains subject matter in common with my application Serial No. 80,718 filed May 20, 1936.

The process described is capable of modification in various ways, and such modificationsare included within the scope of the invention as defined by the appended claims. I

I claim:

1. Process for making a lower alkyl halide from the corresponding dialkyl sulfate and a metal halide, which comprises forming an aqueous solution of a halide of metal whose said halide is capable of dissolving in water in high molar concentrations and whose sulfate is substantially insoluble in concentrated solutions of said halide, said aqueous solution being substantially saturated at least at ordinary temperatures, and heating said solution to between and about 200 C. together with the dialkyl sulfate while maintaining the concentration of said halide in said solution at least at substantially its initial concentration.

2. Process for making a lower alkyl halide from the corresponding dialkyl sulfate and a metal halide, which comprises forming an aqueous solution of a halide of a metal whose said halide is capable of dissolving in water in high molar concentrations and whose sulfate is substantially insoluble in concentrated solutions of said halide, said aqueous solution being substantially saturated at least at ordinary temperatures, and heating said solution to between 90 and about 200 C. together with the dialkyl sulfate while maintaining the concentration of said halide in said solution at least at substantially alkaline materials. Lime has proved to be parits initial concentration by adding metal halide to the solution. '4

3. Process for making a lower alkyl halide from thecorresponding dialkyl sulfate and a metal halide, which comprises forming an aqueous solution of a halide of a metal whose said halide is capable of dissolving in water in high molar concentrations and whose sulfate is substantially insoluble in concentrated solutions of said halide, said aqueous solution being substantially. saturated at least at ordinary temperatures, and heating said solution to between 90 and about 200 C. together with the dialkyl sulfate while maintaining the concentration of said halide in said solution at least at substantially its initial concentration .by removing a distillate containing water from said solution during the reaction.

4. Process for making a lower alkyl halide from the corresponding dialkyl sulfate and a metal halide, which comprises forming 'an aqueoussolution of a halide of a metal whose said halide is capable of dissolving in water in high molar concentrations and whose sulfate is substantially insoluble in concentrated solutions of said halide, said aqueous solution being substantially saturated at least at ordinary temperatures, and heating said solution between about and about C. together with the dialkyl sulfate while removing the alkyl halide from the reaction and maintaining the concentration of the metal halide in said solution at least at substantially its initial concentration by removing a distillate containing the alkyl halide and water. a

5. Processfor making a lower alkyl halide from t the corresponding dialkyl sulfate and an alkaline earth metal halide, which comprises forming an aqueous solution of an alkaline earth metal halide, said aqueous solution being substantially saturated at least at ordinary temperatures, and heating said solution to between 90 and about 200 C. together with the dialkyl sulfate while maintaining the concentration of the alkaline earth metal halide in said solution at least at substantially its initial concentration.

6. Process for making a lower alkyl halide from the corresponding dialkyl sulfate and. an

alkaline earth metal halide, which comprises 1 forming an aqueous solution'of an alkaline earth metal halide, saidaqueous solution being substantially saturated at least at ordinary temperatures, and heating said solution to between about 100 and about 140 C. together with the dialkyl sulfate while removing thealkyl halide from the reaction and maintaining the concentration of the alkaline earth etal halide in said solution at least atsubstant i l halide and water.

7. Process for making a lower alkyl halide from the corresponding dialkyl sulfate and an alkaline earth metal halide in which both alkyl groups of said sulfate are largely caused to react with halogen, which comprises forming an aqueous solution of calcium chloride, said aqueous solution being substantially saturated at least at ordinary temperatures, heating said solution to between 90 and about 200 C. together with the f dialkyl sulfate, and removing the alkyl halide I from the reaction in a distillate.

8. Process for making a lower alkyl halide from the corresponding dialkyl sulfate and an alkaline earth metal halide in which both alkyl groups of said sulfate are largely caused to react with halogen, which comprises forming an aqueous solution of 'calciumbromide, said aqueous solution being substantially saturated at least at ordinary temperatures, heating said solution to between I 90 and about 200 C, together with the dialkyl lly its initial'concentration by removing a distillate containing said alkyl about 200 C.,together with said dialkyl sulfate,

and removing said alkyl halide from the reaction in a distillate.

12. Process for making an alkyl halide of the group consisting of methyl, ethyl, propyl, isopropyl, butyl and isobutyl halides from the corresponding dialkyl sulfate and an alkaline earth sulfate, and removing the alkyl halide from the a reaction in a distillate.

9. Process for making a lower alkyl halide from the corresponding dialkyl sulfateand an alkaline earth metal halide inwhich both alkyl groups of said sulfate are largely caused to'react with halogen, which comprises forming an aqueous solution of barium chloride, said aqueous solution being substantially saturated at least at ordinary temperatures, heating said solution to between 90 and about 200 C. together with'the dialkyl sulfate, and removing the alkyl halide from the reaction in a distillate.

10. Process for making an alkyl halide of thegroup consisting of methyl, ethyl, propyl, isopropyl, butyl andisobutyl halides from the corresponding dialkyl sulfate and an alkaline earth metal halide'in which both alkyl groups of said sulfate are largely caused to react with halogen, which comprises forming an aqueous solution of an alkaline earth metal halide, said aqueous solution being substantially saturated at least at or-' dinary' temperatures, heating said solution to between 90 and about 200 0. together with said metal halide in which both alkyl groups of said sulfate are largely caused toreact with halogen, which comprises forming an aqueous solution of calcium bromide, said aqueous solution being substantially saturated at least at ordinary temperatures, heating said solution to between and about 200 C. together with said dialkyl sulfate, and removing said alkyl halide from the reaction in a distillate.

13. Process for making an alkyl halide of the group consisting of methyl, ethyl, propyl, isopropyl, butyl and isobutyl halides from the corresponding dialkyl sulfate and an alkaline earth metal halide in which both alkyl groups of said sulfate are largely caused to react with halogen. which comprises forming an aqueous solution of barium chloride, said aqueous solution being substantially saturated at least at ordinary temperatures, heating said solution to between, 90 and about 200 C. together with said dialkyl sulfate, and removing said alkyl halide from the reaction in a distillate.

14.Process for making a methyl halide which comprises forming an aqueoussolution of a halide of an alkaline earth metal, said aqueous solution being substantially saturated at least at ordinary temperatures, heating said solution to between 90 and about 200 C. in the presence of dimethyl sulfate, and removing the methyl halide from the reaction in a distillate.

15. Process for making an ethyl halide which I comprises forming an aqueous solution of a halide of an alkaline earth metal, said aqueous solution being substantially saturated at least at ordinary temperatures. heating said solution to between 90 and about 200 C. in the presence of diethyl sulfate, and removing the ethyl halide from the reaction in a distillate.

16. Process for making ethyl chloride which co prises forming an aqueous solution of calcium chloride, said aqueous solution being substantially saturated at least at ordinary temperatures, and heating said solution between about and about 140 C. with diethyl sulfate while removing the ethyl chloride in a distillate.

17. Method of forming ethyl chloride comprising reacting diethyl sulfate with substantially saturated aqueous solutions of calcium chloride at temperatures between about and about ALEXANDER L. WILSON. 

